The Philadelphia Social History Project studies how the nation's second largest city, 1850-1880, was changed by the forces which shaped modern America: Urbanization, Industrialization, and Immigration. More specifically, the research is concerned with the impact of these forces on social mobility, migration, family structure, neighborhood formation, and the development of transportation networks. To this end, a machine- readable data base (numbering several million card images) has been created containing individual level census data (Federal manuscript schedules of population and manufacturing), city business directories, and a complete reconstruction of all means of transportation (trolley, train, omnibus) available to Philadelphians. An interdisciplinary research team, with scholars from history, economics, sociology, demography, and urban geography, are currently analyzing the data base at the University of Pennsylvania.